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THE DEVELOPMENT OF CONTROL SCHEME FOR SINGLE PHASE INDUCTION

MOTOR

SUMI MURNI ZAKARIA

This thesis is submitted as partial fulfillment of the requirements for the award of the

Bachelor of Electrical Engineering (Hons.) (Power System)

Faculty of Electrical & Electronic Engineering

University Malaysia Pahang

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“I hereby acknowledge that the scope and quality of this thesis is qualified for

the award of the Bachelor Degree of Electrical Engineering (Power System) ”

Signature : _____________________________________

Name : MR. RAJA MOHD TAUFIKA RAJA ISMAIL

Date : 29 NOVEMBER 2010

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“All the trademark and copyrights use herein are property of their respective

owner. References of information from other sources are quoted accordingly;

otherwise the information presented in this report is solely work of the author. ”

Signature : _______________________________

Author : SUMI MURNI ZAKARIA

Date : 29 NOVEMBER 2010

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ACKNOWLEDGEMENT

I am greatly thankful to my supervisor, Mr. Raja Taufiqa Raja Ismail for his

advice and guidance throughout my PSM project for two semesters. Thank you very

much.

On top of that, I would like to thank my family member for giving me their loves

and supports throughout my four years study in University Malaysia Pahang.

Special thanks to FKEE lecturers, staffs and all my friends for helping me to

complete my project. Suggestions and criticisms from everyone have always been

helpful in finding solutions to my problems. Thanks you to all.

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ABSTRACT

The purpose of this study is in electronic scope to develop a control scheme for

single phase induction motor application. This project is focus on the AC motor speed

control by varying the duty cycle of Pulse Width Modulation (PWM) signal. PWM

speed control is desirable due to its high power efficiency compare with another method

of speed control like frequency control, current and voltage control. The use of the

control systems can add speed variation to the systems. Control schemes should be

determined based on the control necessary, the cost and the process. The driver circuit

will boosted the PWM signal to drive the MOSFET and thus control the motor. The

speed of AC motor is depending on the spectrum of PWM that refer to their duty cycle.

This project was able to control the motor speed.

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ABSTRAK

Tujuan projek ini dijalankan untuk membina skop kawalan bagi plikasi satu fasa

motor induksi. Projek ini memfokuskn kepada kawalan kelajuan motor AC dengan

mengawal PWM signal. Kawalan kelajuan PWM yang diinginkan bergantung kepada

ketinggian kuasa effektifannya berbanding methodology kawalan kelajuan seperti

kawalan frekuensi, arus and kawalan beza upaya. Kegunaan system kawalan boleh

menambah kepelbagaian kelajuan system. Skema kawalan haruslah ditentukan

berdasarkan kawalan yang diperlukan, kos dan proses. Litar pemandu akan membantu

PWM untuk memandu signal kepada MOSFET seterusnya mengawal kelajuan motor.

Kelajuan motor bergantung kepada spectrum PWM yang merujuk kepada duty cycle.

Projek ini mampu mengawal kelajuan motor.

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TABLE OF CONTENT

TITLE PAGE

DECLARATION ii

DEDICATION iv

ACKNOWLEDMEN v

ABSTRACT vi

ABSTRAK vii

TABLE OF CONTENT viii

LIST OF FIGURES ix

LIST OF TABLES xi

LIST OF SYMBOLS xii

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CHAPTER TITLE PAGE

1 INTRODUCTION 1

1.1 Introduction 1

1.2 Objective of the project 2

1.3 Scope of the project 2

1.4 Problem statement 2

1.5 Project background 3

1.6 Thesis outline 4

2 LITERATURE REVIEW 5

2.1 Introduction 5

2.2 Induction motor 5

2.3 Lead acid battery 7

2.4 Boost converter 8

2.5 Power MOSFET 11

2.6 Inverter 13

2.7 Pulse Width Modulation (PWM) 15

2.8 PI Controller 18

2.9 Matlab 19

3 METHODOLOGY

3.1 Introduction 21

3.2 Block diagram of the project 22

3.3 Designing of Boost converter 22

3.4 Designing of Inverter 25

3.5 Pulse Width Modulation Generation using PIC 18F4550 28

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4 RESULTS AND DISCUSSION 29

4.1 Introduction 29

4.2 Hardware testing 29

4.2.1 Boost converter 30

5 CONCLUSION AND RECOMMENDATION 38

5.1 Conclusion 38

5.2 Future Recommendation 39

5.3 Costing and commercialization 40

REFERENCES 42

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LIST OF FIGURES

FIGURES

NO.

TITLE PAGE

NO.

2.1 Basic boost converter schematic 9

2.2 Boost (a) ON state, (b) OFF state 10

2.3 MOSFET configuration 12

2.4 Basic design of inverter 13

2.5 Simple circuit of inverter 14

2.6 pulse wave, showing the definitions of Y max, Y min and D 16

2.7 Block diagram for controller systems 18

3.1 Block diagram of the project 22

3.2 Circuit design for boost converter 23

3.3 Boost converter output 23

3.4 MOSFET IRF 540N 24

3.5 Model of boost converter 24

3.6 Driver circuit for MOSFET 25

3.7 Basic circuit for inverter 26

3.8 Inverter circuit 26

3.9 18F4550 Microcontroller Pin Configuration 28

4.1 Input for boost converter 30

4.2 Output for boost converter 30

4.3 Inductor 32

4.4 MOSFET with LED 32

4.5 Graph switching MOSFET 33

4.6 Hardware for inverter circuit 35

4.7 Input voltage for inverter 35

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LIST OF TABLES

TABLES

NO.

TITLE PAGE

NO.

4.1 Output obtained from boost converter circuit 31

5.1 Cost of the hardware (Boost circuit) 40

5.2 Cost of the hardware (Inverter circuit) 41

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LIST OF SYMBOLS

C - Capacitor

D - Diode

DC - Direct Current

AC - Alternating current

f - Frequency

kHz - kilo Hertz

L - Inductor

mH - mili Henry

MHz - mega hertz

Mosfet - Metal Oxide Semiconductor Field EffectTransistor

ms - mili second

R - resistor

T - time

V - volt

µs - micro second

µF - micro Farad

Ω - Ohm

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CHAPTER 1

INTRODUCTION

1.1 Introduction

This project is on detailed of control schemes for single phase induction

motor application. The AC induction motor is the most commonly used AC motor in

industrial applications because of its simplicity. It is because the rotor is a self-

contained unit. PICs are popular with both industrial developers and hobbyists alike

due to their low cost, wide availability, large user base, extensive collection of

application notes, availability of low cost or free development tools, and serial

programming (and re-programming with flash memory) capability. The use of the

control systems can add speed variation to the systems. Control schemes should be

determined based on the control necessary, the cost and the process. Pulse Width

Modulation (PWM) techniques is commonly used in a variable frequency drive

scheme to control the rotational speed of an induction motor.

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1.2 Objective of the project

The objectives of this project are

i) To develop a boost converter that convert DC input voltage to

higher DC output voltage.

ii) To develop an inverter that convert dc to ac

iii) To control the speed of the single phase induction motor by

varying PWM

1.3 Scope of the project

This project is developed by using input of 12V battery. Boost converter are

used to convert DC to DC and step up the voltage. Then an inverter is used to

convert the DC to AC voltage. A single phase induction motor is connected to the

end of the inverter.

1.4 Problem statement

The induction machine is the most widely used machine in industry and is

referred to as the work horse of industry. Induction motor is commonly used because

of its simplicity, rugged construction and relatively low manufacturing costs. Single

phase induction motor is used for very small commercial application such as buffers.

So, it is important to control the motor speed in order to achieve a good production.

One of the methods that can be used to control speed of the motor is varying PWM.

Manual controller is also not practical in the technology era because it can waste

time and cost. Operation cost regarding controller is got attention from industrial

field.

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1.5 Project background

This section will describe the overview of this project

1.5 .1 Single phase induction motor

Three-phase motors produce a rotating magnetic field. However, when only

single-phase power is available, the rotating magnetic field must be produced using

other means. Several methods are commonly used. A common single-phase motor

is the shaded-pole motor, and is used in devices requiring low starting torque, such

as electric fans or other small household appliances. Single phase motor are

manufactured in fractional kilowatt range to be operated in single phase supply and

for use in numerous applications like ceiling fans, food mixer, hair drier, portable

drills, vacuum cleaners and electric shavers.

1.5.2 Pulse Width Modulation

Pulse width modulation (PWM) is a very efficient way of providing

intermediate amounts of electrical power between fully on and fully off. A simple

power switch with a typical power source provides full power only, when switched

on. PWM is a comparatively recent technique, made practical by modern electronic

power switches. Pulse width modulation is used to control the frequency and the

magnitude of the AC voltage across the load and to reduce the harmonic contents in

the output voltage or current. There are number of PWM techniques, but the most

common type is the sinusoidal PWM. PWM works well with digital controls,

which, because of their on/off nature, can easily set the needed duty cycle. PWM

of a signal or power source involves the modulation of its duty cycle, to either

convey information over a communications channel or control the amount of power

sent to a load.

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1.5.3 Methodology

The first method is simulation circuit using Orcad. The circuit is simulated

to get expected output waveform at test points and it is compared to the theory. The

second method is constructing the circuit on breadboard. The circuit is tested to get

expected result base on theory. The third method is designed a PIC programmed

that can control the speed of the single phase induction motor. The 12v lead acid

battery is used as a supply. Then the boost converter is use to get the higher output

voltage. Then the inverter is use to convert the dc voltage to ac voltage.

1.6 Thesis outline

This thesis is divided into six chapters. The content of each chapter is

summarized below.

Chapter 1 discusses the overview of the concept of this project, objective of

the project and scope of the project.

Chapter 2 describes briefly the hardware components used in this project,

including their description of operation and article review of the project.

Chapter 3 focuses on the methodology of this project which includes the

generation of the power supply, generation of PWM waveform and full diagram of

the circuit.

Chapter 4 elaborates in detailed about the designing step of boost converter,

pulse width modulation generation and PI controller.

Chapter 5 focuses on the results obtain from the simulation design using

Orcad and the results that obtain from hardware design.

Chapter 6 describes the conclusion, the future recommendation and the

costing and commercialization of the project.

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CHAPTER 2

LITERATURE REVIEW

2.1 Introduction

This chapter will describes in details about induction motor, lead acid battery,

boost converter, inverter, PI controller and Pulse Width Modulation. All those

elements are use to develop this project.

2.2 Induction motor

An induction motor (or asynchronous motor or squirrel-cage motor) is a type

of alternating current motor where power is supplied to the rotor by means of

electromagnetic induction. An electric motor converts electrical power to mechanical

power in its rotor (rotating part). In an induction motor, both the stator and the rotor

windings carry alternating currents. The alternating current is supplied to the stator

directly and to the rotor by induction and hence the name induction machines [1].

Induction motors are often reliable and maintenance is often the first choice when

failure or preventing failure [2].

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2.2.1 Single Phase Induction motor

A motor that operates on a single-phase source is called a single phase

induction motor. A single phase induction motor requires only one single phase

winding to keep the motor running [3]. The single phase motor needs to have high

starting torque as well as high efficiency. But there is trade-off between efficiency

and starting torque. Most single-phase induction motors are built in the fractional-

horsepower range and are used in heating, cooling, and ventilating systems [4]. For

small motors of a few watts the start rotation is done by means of a single turn of

heavy copper wire around one corner of the pole.

2.2.1.1 Shaded pole motors

Shaded pole motors used as a shaded stator pole for starting. Shading the

stator pole is the simplest method used to start a single phase motor. Shaded-pole

motor are commonly 1/20 HP or less and have low starting torque. Common

applications of shaded pole motors include small cooling fans found in computers

and home entertainment centers. The shaded pole is normally a solid single turn of

cooper wire placed around a potion of the main laminations [5].

2.2.1.2 Split-phase motors

A split-phase motor is a single phase motor that includes a running

winding (main winding) and a starting winding (auxiliary winding). Split phase

motors are AC motors of fractional horsepower, usually 1/20 HP to 1/3 HP. Split

phase motors are commonly used to operate washing machines, oil burners and

small pumps and blowers. A split phase motor has rotating part (rotor), a

stationary part consisting of the running winding and starting winding (stator) and

a centrifugal switch that is located inside the motor to disconnect the starting

winding at approximately 60% to 80% of full load of speed. A continuous-duty

motor must operate at full load or 1 hour or more in a 24 hour period. [5]

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2.2.1.3 Capacitor-phase motors

A capacitor motor is a single phase motor that includes a capacitor in addition to

the running and starting windings. Capacitor motor sizes range from 1/8 HP to 10 HP.

Capacitor motor are used to operate refrigerators, compressor, washing machines and

air conditioners. The construction of a capacitor motor is similar to that of a split

phase motor except that in a capacitor motor, a capacitor is connected in series with

the starting winding. The addition of a capacitor in the starting winding gives a

capacitor motor more torque than a split-phase motor. The three types of capacitor

motors are capacitor start, capacitor run and capacitor start and run motors [5].

2.3 Lead Acid Battery

Lead-acid batteries, invented in 1859 by French physicist Gaston Planté, are the

oldest type of rechargeable battery. Despite having a very low energy-to-weight ratio

and a low energy-to-volume ratio, their ability to supply high surge currents means that

the cells maintain a relatively large power-to-weight ratio. These features, along with

their low cost, make them attractive for use in motor vehicles to provide the high current

required by automobile starter motors.

Lead acid batteries designed for starting automotive engines are not designed for

deep discharge. They have a large number of thin plates designed for maximum surface

area, and therefore maximum current output, but which can easily be damaged by deep

discharge. Repeated deep discharges will result in capacity loss and ultimately in

premature failure, as the electrodes disintegrate due to mechanical stresses that arise

from cycling. A common misconception is that starting batteries should always be kept

on float charge. In reality, this practice will encourage corrosion in the electrodes and

result in premature failure. Starting batteries should be kept open circuit but charged

regularly (at least once every two weeks) to prevent sulfation.

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Lead-acid batteries are the oldest type of rechargeable battery. The lead-acid

battery has many advantages over other rechargeable batteries [6]. The most important

for cavers being: fairly high power to weight ratio; low cost; high electrical efficiency

(important where lamps are being recharged from vehicle batteries) flat discharge

voltage characteristics; simple self-service charging capability; and finally, the

electrolyte is far less dangerous than that used in alkali batteries, although the acid will

affect the strength of nylon equipment. On the other hand, lead-acid batteries are perhaps

more susceptible to incorrect charging than alkali types, though if the right method is

used overcharging cannot occur and reliable performance should be obtained [7].

Despite having a very low energy-to-weight ratio and a low energy-to-volume ratio,

their ability to supply high surge currents means that the cells maintain a relatively large

power-to-weight ratio. These features, along with their low cost, make them attractive

for use in motor vehicles to provide the high current required by automobile starter

motors.

2.4 Boost converter

In this project, a boost converter will use to increase the value of DC input

voltage. A boost converter is a DC to DC converter with an output voltage greater than

the source voltage. Since power (P = VI) must be conserved, the output current is lower

than the source current. It is a class of switching-mode power supply (SMPS) containing

at least two semiconductor switches (a diode and a transistor) and at least one energy

storage element. Filters made of capacitors (sometimes in combination with inductors)

are normally added to the output of the converter to reduce output voltage ripple. Boost

converters can increase the voltage and reduce the number of cells.

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2.4.1 Operating principle

The key principle that drives the boost converter is the tendency of an inductor

to resist changes in current. When being charged it acts as a load and absorbs energy

(somewhat like a resistor), when being discharged, it acts as an energy source

(somewhat like a battery).

Figure 2.1: Basic boost converter schematic

Figure 2.1 shows the basic schematic for boost converter. The switch is

typically a MOSFET, IGBT, or BJT.

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(a)

(b)

Figure 2.2: (a) ON state, (b) OFF state

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In the On state as in Figure 2.2 (a), the switch is closed, resulting in an increase

the inductor current. The inductor current increase during the ON state is given by:

∆I = ( )

x + T (1)

The quantity ∆I is the inductor ripple current. During this period, all of the

output load current is supply by output capacitor C1. When the switch is open as in

Figure 2.2 (b), the only path offered to inductor is through the flyback diode D2, the

capacitor C1 and the load R1. This result in transferring the energy accumulated during

the on-state into the capacitor. During OFF state, the voltage across inductor is

constant and equal to ( V + V + I R ) − V . The inductor current decrease

during the OFF state is given by:

∆I = ( )

x + T (2)

The quantity of the ∆I is also the inductor ripple current.

2.5 Power MOSFET

MOSFET is known as the metal-oxide-semiconductor field-effect. Transistor is a

device used to amplify or switch electronic signals. There are two type of MOSFET

which is n type n p type.

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Figure 2.3 MOSFET configuration

Figure 2.3 shows the basic configuration of power MOSFET. It shows that when

electrical bias applied to the gate G, no current can flow in either direction in the gate

because there will always be a blocking p-n junction.

2.5 .1 Advantages of MOSFET

MOSFET has more advantages than other switching devices. Some of the

advantages of MOSFET are listed below.

(i) Low gate signal power requirement. No gate current can flow into the gate after

the small gate oxide capacitance has been charged.

(ii) Fast switching speeds because the channel opens very fast when electron starts to

flow.

S

D

G